In the manufacture of integrated circuits, the standards on interconnecting technology are being upgraded, which require one layer to be deposited on another, resulting in an irregular topography formed on the substrate surface. One planarization method used in prior art is chemical-mechanical polishing (CMP). CMP is a process that uses a mixture comprising abrading grains and a polishing pad to polish the surface of an integrated circuit. In a typical chemical-mechanical polishing method, a substrate directly contacts a rotating polishing pad and a pressure is applied on the back of the substrate by a load. During polishing, the pad and the platform are rotating, the downward pressure applied on the back of the substrate is kept, an abrading agent and a chemically active solution (typically called as a slurry) are applied on the pad, and a chemical reaction occurs between the slurry and the polishing film, so that the process of polishing is initiated.
A CMP polishing slurry typically comprises abrading grains, for example, slurries prepared from alumina abrading grains, sulfuric acid, nitric acid, acetic acid and deionized water as disclosed in U.S. Pat. No. 4,789,648 to Beyer et. al. U.S. Pat. No. 5,391,258 discloses a slurry for polishing a composite of a metal and silicon dioxide, which comprises water media, abrading grains and anions for controlling the speed at which silicon dioxide is removed. Other polishing slurries for CMP are described in U.S. Pat. No. 5,527,423 to Neville et. al., U.S. Pat. No. 5,354,490 to Yu et. al., U.S. Pat. No. 5,157,876 to Medellin et. al., U.S. Pat. No. 5,137,544 to Medellin et. al., and U.S. Pat. No. 4,956,313 to Cote et. al.
As insulating materials having low dielectric constants k are introduced into chips, there is an urgent need for improving conventional CMP polishing slurries, since most of the materials having low dielectric constants are readily cracked. With respect to CMP slurries, it is desired to decrease the concentration of the abrading grains and reduce the downward pressure, in order to eliminate or minimize the defects while keeping a high removing speed.